It is not uncommon for a piping system that contains a high temperature fluid to employ specialized seals at various points in the system. Such points may be found where a connection is made between two or more adjacent piping sections and/or where a component is connected to a section of pipe. When a flexible coupling is used in a piping system, the coupling will typically feature at least one specialized seal.
A jet aircraft's bleed air system is an example of a piping system that employs specialized seals. The system fluid, high temperature air, is bled from at least one of the plane's engines and travels through a duct/piping system within the aircraft to accomplish various functions, such as engine cooling, control of the cabin temperature, and de-icing of portions of the plane's exterior surface. It should be noted that the words pipe, duct, conduit, tube and tubular structure are herein considered interchangeable and all refer to a tubular structure, or even a cylindrical opening, through which a fluid can travel.
Typically, a bleed air system will employ at least one flexible coupling (also commonly known as an alignment joint, a flexible joint, a slip joint, an expandable coupling and a flexible connection) to flexibly connect adjacent duct sections, and/or to connect a section of duct to a component, such as a jet engine. The coupling includes structure that enables it to compensate for misalignments of the ductwork and elongation or contraction of the ductwork brought about by temperature changes. The coupling can also enable the piping/duct system to compensate for movements of the engine or aircraft structure due to various factors including vibration, changes in engine speed and/or loading, and air turbulence.
In the prior art, a number of different specialized seals have been employed in flexible couplings used in aircraft bleed air systems. Since the air flowing through such a system can have a temperature above 600 degrees Fahrenheit, many of these prior art specialized seals take the form of multi-component sealing systems. These systems feature multiple seal rings that are each made of a heat-resistant material and are typically in the form of an annulus.
An example of a flexible coupling used in a bleed air system is taught by Camacho et al in U.S. Pat. No. 5,106,129 entitled Flexible Coupling for Transferring a Fluid Between Two Fluid Conduits. Camacho et al teaches a sealing system that makes use of a pair of seal rings located in a side-by-side relation that overlie a pair of similar width expander rings, that are also deployed in a side-by-side relation. To enable diametrical changes in the seal rings, each seal ring is a split ring by virtue of a thru-cut. In order to discourage leakage, said thru-cut is made using a complex zigzag type of step-cut, such as indicated by lap joint 152 in the patent's FIG. 4. Located beneath the expander rings are two similar width metal split springs.
Another example of a flexible coupling used in a bleed air system is provided in my prior patent, U.S. Pat. No. 6,179,339, entitled Seal Rings for Low Loss Flexible Coupling of Gas Conduits. The patent notes that over time, prior art seal rings can lose their effectiveness. The patent teaches combining a seal ring with a garter spring whereby the spring functions to continuously apply pressure on the seal ring. In this manner, the seal ring's contact with adjacent structure is maximized for a prolonged period of time. It should be noted that to discourage leakage, the split in each seal ring employs a step-cut.
When a piping system has a coupling in which fluid is leaking past a seal ring, the usual method to restore system integrity involves replacement of the seal ring(s). In a typical jet aircraft, replacing a seal ring can be both costly and time consuming, especially if the aircraft is caused to be out of service for a period of time.
It is a first object of the invention to provide a sealing system that is highly effective at preventing fluid leakage.
It is a second object of the invention to provide a sealing system that is extremely durable and can prevent fluid leakage for an extended period of time.
It is a third object of the invention to provide a sealing system that can absorb some of the loads that may be created at a seal point due to vibration, piping misalignment, and piping movements.
It is a fourth object of the invention to provide a sealing system that is relatively inexpensive to fabricate since the split in each seal ring employs a simple butt-cut in lieu of a complex step-cut.
It is a fifth object of the invention to provide a sealing system that is relatively easy to install.